See this is where it can get costly and difficult because while the 02 sensor is a likely cause, there are also many other possibilities that lurk. Another possibility is the crankcase vent valve or any type of vac. leak. The fuel smell could be because of either. If there is a vacuum leak or a bad maf (any type of lean condition) then the DME is going to correct this by dumping more fuel which will cause the 02 sensor to go frantic. Same possibility with a coolant temp sensor. All the added fuel will then create the fuel smell. However, a bad catalytic converter can do the same just in a slightly different fashion. I could go on and on, just too hard to quickly diagnose the problems that you're having without fault codes.